At least 31 people presumed dead on erupting Japanese volcano

At least 31 people are presumed dead after rescuers found them showing no signs of life Sunday near the summit of a Japanese volcano that started erupting a day earlier, CNN reported.

Police said the people were in a state of "cardiac arrest," meaning that they were discovered without a pulse and weren't breathing but hadn't been declared dead by a doctor.

A coroner confirmed the first four deaths Sunday.

Rescue teams had begun searching Sunday for dozens of climbers who were caught by the sudden eruption of Mount Ontake.

The volcano in central Japan unleashed a huge cloud of ash late Saturday morning that billowed down the mountainside and engulfed hikers in its path. Witnesses described hearing a sound like thunder when the eruption began.

The exact number of people unaccounted for was unclear, as officials were uncertain how many had already made it off the mountain.